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  1. #1
    Jr. Apprentice
    Join Date
    Aug 2007
    No. central Arkansas

    Default 07 5.3 flex fuel - engine oil

    Owners Manual states that ONLY 5w-30 weight oil is to be used in this engine. Never seen this limitation before. Guess it has to do with the aluminum engine block or something. Anyone know why?

    P.S. 07 1500 Suburban 4x4.

  2. #2


    I read a bit about it. I think there are several reasons, but I don't recall off the top of my head.

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  3. #3
    Jr. Mechanic
    Join Date
    Sep 2007
    Los Angeles, CA


    The newer engines, having tighter tolerances, require thinner oils. It has to do with the newer, more precise manufacturing technologies, and the fact that thinner oils help better fuel economy. My Bimmer, for example, require 0w-20. I don't know if your truck requires it or not, but I would definitely use synthetic oil!!

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